Modify parser to group html begin/end elements.

- Added a "Tag" block type.
- Wrapped all begin/end elements in a "Tag" Markup block.

#75
Fix tests to work with new TagBlock parsing format.

- These are the fixes to the tests that could not be fixed by altering the core parsing code base.
- Most involve adding TagBlock's, breaking out existing markup blocks and altering some AcceptedCharacter formats.
- Was able to loosen the restrictions on AcceptedCharacter's to allow the body of html tags to accept any character.

#75
Updated to use the new target framework in project.json